APPENDIX. 329 



quent use is still more difficult, yet witk a little patient 

 practice every person can do it satisfactorily. More care 

 should be exercised to secure good specimens, and every air 

 bubble must be expelled. The mounting medium should 

 be, as a rule, glycerine, yet for some objects Canada balsam 

 is better. Other media are used, but the beginner need 

 not now encumber himself with them. Proceed as directed 

 above, but more care must be exercised in putting on 

 the cover-glass, so as not to entrap any air bubbles. The 

 superfluous fluid must also be more carefully removed, and 

 the slide wiped till thoroughly dry; then with a small 

 camel's hair brush, dipped in asphalt or other cement 

 manufactured for this purpose, run a line along the edge 

 of the cover-glass, cementing it to the slide ; set it aside, 

 protected from dust, for a day or two, or till dry, and 

 run another line of cement over the first, and perhaps 

 ultimately a third one to thoroughly secure it. Square 

 cover-glasses will be found to be much more convenient 

 than round ones. The mounted slides must be kept free 

 from dust, for they are difficult to clean. It should be 

 remembered that Lf strong alkalies or acids have been used 

 in the preparation of specimens, they must be thoroughly 

 washed to remove every trace of the reagent, otherwise the 

 specimen will be worthless. Neutralize acids with weak 

 ammonia, and alkalies with acetic acid. Dry mounts are 

 such as are made without the use of any mounting medium. 

 Pollen grains, spores, and a few other objects may be so 

 prepared. For detailed directions for manipulating the 

 microscope, preparing and mounting objects, one must 

 have recourse to the various works on such subjects, and 

 for material of all kinds apply to manufactures and dealers 

 of such wares. It is quite desirable to have small forceps, 



